Package org.apache.cassandra.io.util

Class PageAware

  • public final class PageAware
extends java.lang.Object

    • Constructor Summary

      Constructors 
      Constructor Description
      PageAware()  

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static int bytesLeftInPage​(long dstPos)
      Calculate the number of bytes left in this page.
      static int numPages​(int size)
      Calculate the number of pages that fit in the given size, rounded up to a page if the size is not an exact multiple.
      static void pad​(DataOutputPlus dest)
      Pad the given output stream with zeroes until the next page boundary.
      static long padded​(long dstPos)
      Calculate the earliest page boundary for the given position.
      static long pageLimit​(long dstPos)
      Calculate the end of the page identified by the given position.
      static int pageNum​(long dstPos)
      Given a position relative to the start of a number of pages, determine the exact page number this position falls into.
      static long pageStart​(long dstPos)
      Calculate the start of the page that contains the given position.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • PAGE_SIZE_SHIFT

        public static final int PAGE_SIZE_SHIFT

    • Constructor Detail

      • PageAware

        public PageAware()

    • Method Detail

      • pageLimit

        public static long pageLimit​(long dstPos)
        Calculate the end of the page identified by the given position. Equivalent to floor(dstPos / PAGE_SIZE + 1) * PAGE_SIZE.

        When the argument is equal to the page boundary, returns the next page boundary. E.g. pageLimit(0) == PAGE_SIZE.

      • pageStart

        public static long pageStart​(long dstPos)
        Calculate the start of the page that contains the given position. Equivalent to floor(dstPos / PAGE_SIZE) * PAGE_SIZE.

      • padded

        public static long padded​(long dstPos)
        Calculate the earliest page boundary for the given position. Equivalent to ceil(dstPos / PAGE_SIZE) * PAGE_SIZE.

        When the argument is equal to a page boundary, returns the argument.

      • bytesLeftInPage

        public static int bytesLeftInPage​(long dstPos)
        Calculate the number of bytes left in this page. Equivalent to pageLimit(position) - position.

        When the argument is equal to a page boundary, returns PAGE_SIZE.

      • numPages

        public static int numPages​(int size)
        Calculate the number of pages that fit in the given size, rounded up to a page if the size is not an exact multiple.
        Parameters:
        size - the size that needs to cover a number of pages
        Returns:
        the number of pages, rounded up

      • pageNum

        public static int pageNum​(long dstPos)
        Given a position relative to the start of a number of pages, determine the exact page number this position falls into. For example, positions from 0 to PAGE_SIZE -1 will fall into page zero and so forth.
        Parameters:
        dstPos - the position
        Returns:
        the page number, indexed at zero

      • pad

        public static void pad​(DataOutputPlus dest)
                throws java.io.IOException
        Pad the given output stream with zeroes until the next page boundary. If the destination position is already at a page boundary, do not do anything.
        Throws:
        java.io.IOException